Garden School:


Garden School:
Teaching this week: Basic tool fitting - right tool, right size.

Sunday, 19 August 2018

Cherry tree with damaged bark

I had a question come in the other day, about a small ornamental Cherry with damage to the bark - a whole section of the bark at about chest height was peeling away, and the anxious owner was worried that the tree would die.

Here's a picture of the tree, taken earlier this year: as you can see, quite a big area of damage.


So why did this happen, and what can be done?

Well, the first thing to say is that Cherries are not long-lived trees: an ornamental one can have a lifespan as short as 20 years, which is no time at all in the life of a garden, especially if we buy them when they are four or five feet tall, which means they are already five years old before we get them.

So if you have a Cherry that's been there for more than a decade, it may well be heading towards the end of its life anyway.

The actual damage could have occurred for many reasons: it could be frost damage, where water gets inside a small split in the bark, then freezes. As it expands, it splits the bark.

The original split may have been disease: cherries are susceptible to phytopthera and to bacterial infection, and there's not much we, as garden owners, can do about it - the spores are "in the air" as it were, and there is no way to prevent them wafting in.

Canker is another possible cause: if the crack in the bark is accompanied by a gummy substance or a darkened crust, then the tree may be infected with one of the many fungal diseases known collectively as canker. Like phytopthera, cankers are always hanging around looking for an opportunity, and trees that are stressed due to frost damage, mechanical injury or lack of water are more likely to develop canker.

If you spot any heavily cankered branches, the best thing to do is to prune them out, making sure that diseased branches are burned or destroyed, to prevent the disease from spreading right back into the tree, and into others nearby.

Going back to frost damage, a little internet research suggests that after a chilly winter night, the south- and east-facing sides of a cherry tree may split as the morning sun causes the bark to warm, expand and break.  If this occurs, the tree will heal on its own, but it forms callused scabs, which are less than pretty. To prevent this, the internet suggests that we paint the trunk with whitewash to help reflect light, making sure to do this only when the trunk has no open wounds. I'm not sure I'd actually go that far, myself, would you?

Apparently you can also "wrap the tree with plastic, paper or cardboard to keep it warm while it heals."   Personally I would not wrap any living plant in plastic, as it "sweats" which would worsen the problem. And I'm not keen on wrapping any plant in anything, for that matter, because you are creating a bug hotel which may well be ecologically very sound, but is likely to lead to even more damage to the bark. So much for the internet, then!

Another possibility for damaged bark is herbicide Injury: many weedkillers contain a wetting agent that can cause permanent damage in thin-barked trees, such as cherry trees, especially when the trees are young. So if you have to use weedkiller near your trees, try to stay at least 20-30 feet away from the trunk (not always possible, I know), and only ever do it on calm, still days, so that the wind doesn't waft the spray over onto the trees.

If it makes you feel any better, I have this tree near to where I live:

As you can see, the bark is split so dramatically that it's practically hanging off the trunk, and the damage extends well over 50% of the trunk diameter.

Yet it's been like this for at least five years, and so far the tree keeps soldiering on, undaunted, which is probably a lesson to us all in persistence in the face of adversity.

So is there anything we can do to prevent these problems occurring in the first place?

Yes: healthy, stress-free cherry trees are far less likely to succumb to problems such as splitting bark than trees that are poorly taken care of.

If you are thinking of planting a new Cherry tree, wait until early spring: trees planted then will have plenty of time to develop a strong, healthy root system before winter sets in.

Plant them carefully: prepare a good, big hole, make sure it's the right depth, and make sure you don't damage the trunk when you manhandle it into the hole, especially if it's a largeish one.

Be careful with stakes and ties: never, ever nail or screw the tree tie to the tree (don't laugh, I've seen it done), and check the ties every year to make sure they are not getting too tight.

Water and feed your new tree for the first year, and in subsequent years, if we have prolonged dry periods, give it a bucket of water every couple of days.

Be nice to your tree: if it's planted in grass,  make a clear space all around it for a foot or more - grass is terribly competitive for water and nutrients, and both fruit trees and ornamentals dislike having to compete for these essentials.

There's another good reason for making a small "bed" around their base: many bark problems are caused by damage from strimming or mowing, so if you have a small clear area around the base of each tree, it will reduce the risk of banging the mower into the trunk, or of whipping it bare with a strimmer.

So there you go: damaged bark on ornamental cherries can be prevented - to some extent - by keeping the tree healthy and un-stressed: and if the worst does happen, it's not always fatal. Or at least, not straight away!